1. Field of the Invention
The present invention relates to a method for forming an electrode pattern on the surface of ceramic electronic parts made of sintered ceramic and more particularly to a method for forming input-output electrodes of dielectric resonators.
2. Description of the Related Art
Conventionally, dielectric resonators made of a sintered ceramic material composed of dielectric ceramic are known. Such types of dielectric resonators include, for example, dielectric coaxial resonators with through holes made in a dielectric block formed from a sintered ceramic material, inner conductors each formed on the inner peripheral surface of one of the through holes, and an outer conductor provided on the outer surface of the dielectric block. Furthermore, input-output electrodes are formed on the outer surface of the dielectric block such that they are electrically insulated from the outer conductor.
Conventionally, various methods have been employed for forming the above-mentioned outer conductor and input-output electrodes.
The first method is carried out as follows: on the outer surface of a dielectric block, a resist is applied to a region between regions where the input-output electrodes are to be formed and a region for forming the outer conductor; a conductive film is provided on the entire outer surface of the dielectric block by plating; and then, the resist is removed. According to this method, the conductive film is not formed on the region having the resist thereon. Thus, the input-output electrodes and outer conductor are prepared by removing the resist after plating.
The second method proceeds as follows: a mask is provided on the outer surface of a dielectric block such that regions for forming the input-output electrodes and a region for forming the outer conductor remain uncovered; and then a silver paste, etc. is applied by screen printing so as to form the input-output electrodes and outer conductor.
The third method is disclosed in Japanese Patent Laid-Open No. 6-334414 and carried out as follows: a conductive film is applied on the entire outer surface of a dielectric block by plating; and then, the conductive film is partially removed by contacting it with a cutting tool which is vibrated by an ultrasonic machine so as to separate the film into the input-output electrodes and outer conductor.
The fourth method is disclosed in Japanese Patent Laid-Open No. 7-321519 and carried out as follows: a conductive film is applied on the entire surface of a dielectric block by plating; and then, a resist-masking formed of a resist film material is laminated on part of the conductive film; and then, the part of the conductive film not covered by the resist-masking is removed by sandblasting.
According to the first method, numerous steps, such as resist application, plating, and resist removal, are required for forming the input-output electrodes and outer conductor. As a result, the cost increases because of the use of the resist and the productivity becomes insufficient.
According to the second method, the mask can be repeatedly used and the number of steps is lower than that of the first method. However, since each of the input-output electrodes of dielectric resonators is generally formed over two faces, the input-output electrodes and outer conductor cannot be accurately formed with high productivity by covering the dielectric block with a mask and applying a conductive paste by screen printing.
According to the third method, the input-output electrodes and outer conductor are formed by a simplified process wherein a conductive film is applied on the entire outer surface of the dielectric block by plating, and then, the conductive film is partially removed. However, the step of partially removing the conductive film using the cutting tool vibrated by the ultrasonic machine must be carried out separately for each of the dielectric blocks. In other words, it is impossible to process numerous dielectric blocks at the same time, resulting in insufficient productivity. In addition, since the cutting tools readily get worn out, it is necessary to frequently exchange the tools, and high mounting accuracy is required. Therefore, tool exchange takes a considerably long time-period. As a result, although the process for forming the conductive film is simplified, the productivity of the step for separating the input-output electrodes and outer conductor is insufficient.
According to the fourth method, after the step of laminating the resist-masking on the outer surface of the dielectric block and the step of removing the part of the conductive film not covered by the resist-masking, a cumbersome step using a solvent for removing the resist-masking must be carried out. As a result, like the first method, the cost increases because of the resist material and the resist-masking which can not be used repeatedly, and the productivity becomes insufficient.